Apparatus for producing and receiving signals



MaWch-ll 1924. 1,486,735

' R. A. FESSENDEN APPARATUS FOR'PRODUCING AND RECEIVING SIGNALS FiledAug. 15, 1918 2 Sheets-Sheet l INVENTOR.

BY I ha 61'! ATTORNEYS.

March 11 ,1924. 11,486,735

R. A. FESSENDEN APPARATUS FOR PRODUCING AND RECEIVING SIGNALS FiledAug:- I5, 1918 2 Sheets-Sheet 2 Hal/R53 44 44 fla /#55 IN VEN TOR.

A TTORNEYS Patented Mar. llll, 11924.

UNITED 'STATES insane earner castes.

' REGINALD A. FESSENDEN, OF BROOKLINE, MASSACHUSETTS[ASSIGNOR TSUBMARINE I SIGNAL COMPANY, OF PORTLAND, MAINE, A CORPORATION OF MIAINE.

APPARATUS FOR PRODUCING AND RECEIVING SIGNALS.

Application filed August 15, 1918.

To all whom it may concern:

Be it known that I, REGINALD A. FnssnN DEN, of Brookline, in the countyof Norfolk and State of Massachusetts, a citizen of the United States,have invented new and useful Improvements in Apparatus for Producing andReceiving Signals, of which the following is a specification.

My invention relates to apparatus for producing and detecting signalsand other impulses, and for increasing the efliciency of such generationand reception, and more particularly to submarine signaling, and stillmore particularly to the detection of submarines and similar bodies.

My invention has for its object increased efficiency in the generationand reception of said impulses, and more particularly greater strengthand clearness of generation and reception, and the elimination ofundesired noises.

My invention will be understood by reference to the drawings in which-Figure 1 is a diagrammatic view of appa- 25 ratus and circuits embodyingmy invention,

the microphone being in longitudinal section.

Fig. 1 is a plan showing the pointer turned in a different directionfrom Fig. 1, so and the rheostat circuit.

Fig. 2 is a diagrammatic view in which the microphone is circular.

gig. 3 is a diagrammatic side elevation, an

Fig. 4 a cross section, enlarged, of a ships huiil to which my apparatusis attached, an

Fig. 5 shows in cross section another form of carbon elements arrangedto embody my invention.

Heretofore, microphones have been generally constructed of carbongranules or of pairs of carbon balls or plates, and heretoforemicrophones, consisting of a large number of plates or balls have notbeen used because they have not been found to give useful results.

Applicant has carried on for a number of years an extendedseries ofinvestigations on this subject, and has found that the reason Why suchmicrophones have not been put in use heretofore, although a priori alarge number of contacts in series might be expected to give greaterstrength, is due to the fact that when a column is built up of SerialNo. 249,943.

such plates or .balls, and an impulse is impressed on one end of thecolumn, the density of the column is that of the carbon, buttheelasticity of the column is not that of the carbon, but of the carboncontacts and is of a very much lower order than that of the carbonitself. Y

Consequently, the virtual elasticity of the column being very low, thevelocity of an elastic wave along such a column is very slow, and itsdamping very high. Consequently, if such a column be attached to adiaphragm of a telephone transmitter and a note sounded against thetransmitter having a frequency of, say, 200 (two hundred) per second,the elastic wave will travel along the column of contacts at such a slowrate that there may be a large number (say, 7 or 8) complete waves inthe column, and consequently the reduction in resistance at thecompressional parts of the waves will neutralize the effects of theincreased resistance at the expansional part of the waves; andconsequently, the change in resistance will be no greater or even lessthan that due to a single pair of contacts.

Applicant has discovered in the first place that by clamping these diskstogether under considerable pressure, the virtual elasticity of thecontacts may be very greatly increased, so that the elastic wave willhave many times the usual length in such columns; for example, 50(fifty) times the length, and that consequently increased effects can beobtained in this length.

Applicant has also discovered that where the column is not so clampedunder pressure, or only under moderate or light pressure, advantage maybe taken of the slow propagation of elastic Waves in the column, and theproduction of nodes in the column, to locate the direction from whichthe impulses are received.

Applicant has also discovered that such columns are extremelyinsensitive to disturbing influences, such as the water noises, etc.,such as met in submarine signaling and submarine detection.

Applicant has also discovered that such such as oil, or in anon-conducting tube, such as, for example, one formed of rubber, orchrome gelatine.

In Figure 1 is shown one type of apparatus. Here 11, 11 are carbonplates,

either flat, as shown, or somewhat lens' shaped, as shown at 11, 11', orrounded, as shown at 44, 44, Figure 5. These plates are slipped into arubber, or chrome gelatine, tube, 12, so as to form, with the circulardisk metallic terminals, 45, 46, 47, 48, a column of microphoniccontacts. This column is held in the rubber tube 12 by the rubber corks13, 14, though if desired the microphonic column and its terminals maybe completely encased in unvulcanized rubber, and the column put underthe pressure desired and the rubber vulcanized in place so as to form ahomogeneous unit.

For the purpose of maintaining and regulating the proper tension on thecolumn, a support 29 is provided having one end attached to the rubbercork 13 bearing upon one end of the column and the other attached to therubber cork 14 and bearing upon the opposite end of the column. Thesupport 29 has an air gap at 51 and a coil 52 wound about the support 29and the air gap, the coil 52 extending over the metal of the support 29on either side of the air gap. The current through the coil 52 isregulated by a rheostat 54 in series with a battery 53 which suppliesthe current to the circuit consisting of the battery 53, coil 52, andrheostat 54. When the coil is energized by thecurrent flowing throughit, magnetic lines are induced in the metal support which magnetic linesflow across the air gap within the coil and about the exterior of thecoil thereby completing a circuit about the coil 52. The ends of themetal forming the poles of the air gap are thus magnetized north andsouth respec tively, and thus exert a mutual pull upon each other. Bymeans of the support, this pull is exerted upon the ends of the columnwhich is compressed as a whole. It should be noted that the tube 12 willnot interfere with the appliance of pressure upon the column since thetube is of rubber and is itself easily compressible. From the contacts45, 46, 47, 48 conductors 15, 23, 24, 16 are led. to the switch points20, 21, 22, 230, and a battery 17, and telephone receiver 18 isconnected in one of the leads, for example as shown, the lead 15.

On the microphone column being immersed in water and a sound wave of thefrequency of 1000 (one thousand) per second being transmitted throughthe water, since this sound wave will have a length of approximately 4(four) feet in water, if the microphone column is 8 ft. long, thatis,more than the quarter wave length of the impulse, there will be 2 (two)complete waves acting weaves on the column, and the effect will tend tobe diminished if the switch is thrown so that 230 is connected to 22. Ifthe switch 230, however, is thrown to be connected with 20, a variationin the intensity will be observed from what it was when 230 and 22 wereconnected, and this efiect may be made use of to eliminate undesirednoises, as obviously the best position will not be the same for all wavelengths, and by rotating the switch the most sensitive point for. thedesired wave length can be determined.

In order to obtain direction, the microphone column as a whole may berotated, the shaft 31, and pointer 32 being attached to the steel bar 29and rotatable in the bearing 33. In actual tests it has been found thatwhen the microphonic column is rotated a variation of strength of morethan 400 (four hundred) per cent is obtained, according to whether thecolumn is lying side on or pointing towards the source of sound.

.In place of rotating the column to obtain direction, different sectionsof this microphone lying in different directions or planes may beconnected to the receiver. Figure 2 shows such a type, where the rubbertube 25 is circular in shape thus giving uniform compression all aroundthe circle, and four microphone terminals, 26,27,28,290,are brought outto the switch points, 30, 31, 32, 33, and by rotating the switch, 34,35, the receiver 36 is attached to any pair of contacts desired. In thiscase, therefore, the microphone column is curved instead of straight andits elements function in the same way as in the form shown in Fig. 1. Asuitable location for such microphone rings is shown in Figure 4 at 49,49', where the microphone rings are placed on the bottom of the boat,either slightly to one side as shown at 49, or directly beneath thekeel, as shown at 49.

These methods are therefore valuable also for determining direction ofsound. It has also been discovered that the light, rustling noises andother noises made by the rush of water past the ships side can beentirely eliminated by the above construction, and desired noises, suchas given off by submarines, and especially low notes due to hullvibrations and propellor noises are brought in with greatstrength, andmay be selected, not only from water noises, but also from noises madeby boats running on surface.

This type of microphone may be used in any suitable location; forexample, in a Water ballast tank, or a specially constructed tank, or inthe bilges, or towed overboard, or in oil tanks. A suitable arrangementis shown in Figure 3 and Figure 4, where 40 is the hull of a vessel and42 the bilge keels, shown in cross section in Figure 4. In this method,applicants distributive elastic wave microphone, or F essendenmicrophone, may

against machinery noises, though these have little effect in any case.

Where, however, such machinery noises exist, a sound screen as shown in43, Figure 4;, may be placed around the microphone column with anopening outwards.

While I have herein described the use of this microphone for submarinedetection, it is also of general use for submarine detection and for thegeneration and reception of impulses generally.

'What I claim is 1. Means for submarine signaling comprising. aplurality of plates of microphonic material, arranged as a column, andexposed to the action of the impulses to be received.

2. Means for submarine signaling comprising a plurality of plates ofmicrophonic material, arranged on a dead heat support as a column, andexposed to the action of the impulses to be received.

3. Means for submarine signaling comprising a plurality of plates ofmicrophonic material, arranged as a column, and contained in an elastictube.

4. Means for submarine signaling comprising a plurality of plates ofmicrophonic material, arranged as a column, and a plurality ofelectrodes inserted in the column and exposed to the action of theimpulses to be received.

5. Means for submarine signaling comprising a plurality of plates ofimperfect contact material, arranged as a column and exposed to theaction of the impulses to be received, a plurality of electrodesinserted in the column, and a switching means for interconnecting anydesired terminals.

6. Means for submarine signaling comprising a plurality of plates ofimperfect contact material, arranged as a column in the mediumtransmitting the impulses, said column being longer than the quarterwave length of the impulse which it is desired to receive.

7. Means for submarine signaling comprising a plurality of plates ofmicrophonic material arranged in a column, each plate forming contactwith the face of the adjacent'plate, a plurality of electrodes atintervals in the column forming a plurality of receiving units inseries, an elastic tube enclosing said column, caps closing-the ends ofsaid tube and retaining the column under desired pressure, and switchmeans whereby the number of receiving units in series best adapted forthe wave length of the signal to be received may be used.

REGINALD A. FESSENDEN.

